The present invention relates to dynamic modulation index calibration for near field communication (NFC) devices, and more particularly, to a method for controlling a modulation index of an NFC device, and to an associated apparatus.
According to the related art, a conventional NFC device can be designed to communicate using a predetermined ASK data rate. In practice, it is typically needed to make sure of a proper value of the modulation index in advance (e.g., in a design phase of the conventional NFC device, or during manufacturing the conventional NFC device), in order to achieve better performance of the conventional NFC device. As the modulation index depends on many factors such as the antenna size of the conventional NFC device, the proximity of the target antenna (e.g. the distance between the antenna of the conventional NFC device and the target antenna of another device), and the NFC antenna matching network of the conventional NFC device, some problems may occur. For example, the designer of the conventional NFC device may have designed the conventional NFC device based upon a wrong assumption of the proximity of the target antenna, causing the performance of the conventional NFC device to become unacceptable to the user in some situations. In another example, the manufacturer of the conventional NFC device may need to manually adjust the conventional NFC device for different target value of the modulation index, causing the associated costs such as additional labor costs of manually adjusting the conventional NFC device to be irreducible. In another example, as the modulation index depends on the antenna impedance, and as the antenna impedance is typically sensitive to the environment that shifts its resonance frequency due to magnetic field coupling, in a situation where a metallic surface, a secondary antenna in close proximity, etc. change the antenna impedance drastically, the performance of the conventional NFC device may become unacceptable to the user. Thus, a novel method is required for improving the modulation index control of the NFC device in various kinds of situations.